Our sleep is regulated by daylight and darkness. In the morning hours, our body increases its production of adrenaline and dopamine, while at the same time decreasing sleep-inducing hormones. Adrenaline is a hormone and a neurotransmitter that is produced from amino acids. Dopamine is also a neurotransmitter. This hormonal response to daylight is what allows us to become awake, and alert.
In the evening when it becomes dark, our body begins producing chemicals like serotonin, GABA, and melatonin. Serotonin is a monoamine neurotransmitter, melatonin is a naturally occurring hormone, and gamma-aminobutyric acid is the largest inhibitory neurotransmitter in our central nervous system. It plays a vital role in regulating neuronal excitability throughout our body. All of these chemicals and hormones allow us to relax and prepare for sleep.
There are several stages of sleep that we go through during a typical night. Stage one is characterized by the slowing of our brain activity and the closing of our eyes. In this stage, it is very easy to disturb us, and we awaken as a result.
In stage two, our brain activity is reduced even further, and our muscles begin to relax, Our heart rate slows, and our body temperature decreases. Our skeletal muscle system begins deactivating as our body shuts itself down and prepares for deep sleep.
In stages three and four, our brain activity reduces even further. We also experience complete skeletal muscle paralysis, loss of environmental awareness, and our metabolic functions slow down as well. Stage three moves into stage four, which is the deepest sleep that we experience. It is likely the most beneficial in regards to recuperation, and muscle growth, as this is the stage that growth hormone levels hit their peak.
REM sleep, or Rapid Eye Movement sleep, often referred to as stage five sleep, is characterized by rapid back and forth eye movement, as well as extremely vivid dreams. In this stage, our heart rate actually increases, as does our blood pressure, and our breathing also becomes more rapid.
As we advance throughout the night, we enter in and out of the various stages. Sleep is, of course, an extremely important factor in our health, not to mention in the growth of our muscles. Later on I’ll get into more on the value of sleep for our muscles.